Left 4 Dead shifts 2.5m at retail

Valve, the developer of co-operative zombie shooter Left 4 Dead, has revealed that its title has sold over 2.5m units worldwide at retail since launch, Edge reports.

The number includes boxed sales of the game on both Xbox 360 and PC.

The figure doesn't include sales of the game through Valve's highly successful online digital distribution portal Steam. Valve announced earlier this year that following a 50 per cent promotional discount to the game on Steam, sales rocketed by an impressive 3,000 per cent.